The present invention relates to a mechanical governor for a fuel injection pump for use in internal combustion engines and, more particularly, to a mechanism for adjusting reaction force acting upon a governor control lever.
A fuel injection pump for internal combustion engines such as a diesel engine and the like comprises a control rack connected to a plunger of the injection pump, for regulating the fuel injection amount injected thereby. Movement of the control rack is controlled by a mechanical governor which, in general, utilizes centrifugal force and which actuates the injection pump in such a manner as to maintain a predetermined relationship between the fuel injection amount from the injection pump and the engine rotational speed. The mechanical governor comprises a governor control lever connected to an accelerator pedal for displacing the control rack in response to a depression amount of the accelerator pedal.
In general, a single main spring is attached to the governor control lever, which serve as return biasing force accumulating means for biasing the control lever in such a direction as to return or release the accelerator pedal, to return the control lever with high response at the shift of the accelerator pedal from its depression position to its lease position. It is required to apply appropriate biasing force or reaction force in the return direction to the governor control lever in accordance with its angular position. With the above-described arrangement having the signal main spring, however, such a situation would arise that the biasing force acting upon the governor control lever in the return direction increases proportionally in accordance with increase in the angular position or lever angle of the control lever. More specifically, as the lever angle of the governor control lever becomes smaller, the biasing force of the main spring gradually diminishes. Thus, the reaction force applied to the governor control lever gradually decreases, so that the return characteritic of the control lever or responsiveness with which the control lever returns becomes deteriorated. On the other hand, as the lever angl becomes larger, the reaction force applied to the control lever gradually increases, so that the biasing force of the main spring which pulls the control lever in the returning directing greatly inoreases and as a result a very large force or accelerator pedal-stepping force is required to maintain the control lever in a desired angular position in which the lever assumes a large angle. This results in degradation in operability of the control rack with respect to movement of the accelerator pedal.
To cope with the aforesaid situation. a lever reaction force-reducing device has been proposed, e.g. in Japanese Utility Model Publication (Kokoku) No. 54-4583, in which a balance spring is employed for applying, to the control lever, a moment acting in a direction opposite to the direction of the reaction force acting upon the control lever due to the main spring, to reduce the reaction force in proportion to the lever angle of the control lever. In the lever reaction force-reducing device, one end of the balance spring is fixedly secured to a casing of the mechanical governor, and the other end of the balance spring is connected to the control lever through an adjusting plate member such that the other end is angularly movable relative to the one end in response to pivotal movement of the control lever. Thus, a line of action of tension of the balance spring is pivotally displaced about the one end of the balance spring in response to pivotal movement of the control lever so as to move across the pivotal axis of the control lever, in order that the gradually increasing or decreasing biasing force of the main spring is gradually reduced or increased in accordance with the pivotal displacement of the line of action, depending upon the line of action is located on one side of the pivotal axis of the control lever or on the opposite side thereof. With such lever reaction force-reducing device, however, the freedom or range of movement of the balance spring is small, because the one end thereof is fixedly secured to the casing of the mechanical governor. Therefore, it is not possible to sufficientIy secure a range of variation in the moment produced by the tension of the balance spring and its distance of action which moment is necessary for reducing the reaction force acting upon the governor control lever. There is, as a matter of course, a limit in an extent within which it is possible to appropriately reduce the reaction force acting upon the control lever due to the main spring. In particular, since the maximum value of the aforesaid moment is low, it is difficult to reduce the reaction force when it is maximum. Thus, the operability of the control lever still remains to be improved.